1. Field of the Invention
The present invention concerns improvements in weft feeders for gripper or projectile looms, allowing an operator promptly to restore the continuity of the weft yarn from the yarn feed spool or reel to the members for weft insertion into the loom shed, in case of yarn breakage or interruption.
2. Description of the Related Art
In most cases, in the event of yarn breakage, it is necessary to introduce a new weft yarn into the weft feeder, that is, to perform a series of operations by which the free weft yarn end, fed from the spool or reel, is guided into the various passages provided therefor in the weft feeder, so as to be then readily introduced into the loom weft insertion members.
FIG. 1 of the accompanying drawings shows the prior art weft feeder configuration to which reference is made in the description given hereinafter of the invention. The weft yarn 1, drawn from the spool 2, is guided through an eyelet 3 into the inner cavity of the winding arm 5 which, moved by an electric motor 4, winds it up into even turns around the winding unit or drum 6. The weft yarn 1 is then unwound from said drum 6 in an axial direction--drawn by the loom weft insertion members--and it is braked by known type brake means, consisting of a ring 7 carrying an annular brush 8, whose bristles press--with an adjustable pressure--against the round-shaped periphery of the drum 6. The weft yarn 1 is finally let out through a guide eyelet 10, centered on the drum axis and carried by a radial bracket 9 positioned alongside the drum 6. Downstream of the yarn guide eyelet 10, use is often made--to improve and complete the action of the annular brush brake 8--of a double-leaf brake 21, and/or of a weft tension device 31, comprising an oscillating lever, useful especially in gripper looms; both these devices--known per se--are carried by the same bracket 9 and are positioned in alignment with the eyelet 10 on the drum axis.
According to conventional technique, the previously described operation of introducing a new weft yarn into the weft feeder is carried out manually--with the help of a flexible threading hook which, as known, consists of a strip of flexible material ending with a slot or hook--and it is a rather long and toilsome operation which also requires a certain experience. Several expedients have so far been adopted to facilitate the insertion of a new weft yarn by means of a threading hook, for instance forming guides of various types allowing a quicker and safer introduction of the threading hook, as described for example in DE-2932782 and in EP-285592: according to this latter, the threading hook is used to insert the weft yarn also in the double-leaf brake and in weft tension device.
In the attempt to make the above operation more automatic, it has more recently been proposed to introduce a new weft yarn into the weft feeder by means of compressed air jets, as described for example in DE-G-8712946, wherein successive yarn launching and guiding devices are provided to insert the yarn into the various passages, without the help of a threading hook. The most critical and difficult part is however the pneumatic introduction of the yarn into the guide eyelet 10, at the outlet of the weft feeder, in that very sharp deviations have to be imparted on the yarn in order to guide it from the drum periphery into said eyelet 10.
According to EP-A1-436900, filed by the Applicant the introduction of the yarn into the guide eyelet 10 is efficiently obtained by positioning said eyelet along the rectilinear trajectory of the yarn coming out from a duct provided downstream of the winding arm, and by simultaneously removing the annular brush brake from its working position, so that the yarn, passing through the ring 7 of said brake, is then introduced into the eyelet 10. This system fully solves the above problem, but it supplies a solution which forms part of a totally automatic system to restore the continuity of the weft yarn from the spool to the loom; furthermore, it does not consider introducing the yarn into any additional devices--such as the double-leaf brake and the weft tension device--which, as already said, may often be provided (especially in gripper looms) downstream of the yarn guide eyelet 10, at the outlet of the weft feeder.